I think very usefull features (Conditional field) if it can be applied.

For example:

I've a field called Colors ( any field type such as Radio, CheckBox or Dropdownd field), It can be extendable/changable for other purpose.:
And I have a couple options such as Blue, Red, Green and Other. If user select Other option, a text field will shows for enter user's own value.

Sorry for my bad english. I hope, it is clean explained.